1. Field of the Invention
The present invention relates to multistage comparators used in analog-to-digital converters (ADCs), and more particularly relates to methods for calibrating such multistage comparators to remove the native comparator offset and charge injection offset resulting from the opening and closing of input switches during the sampling operation.
2. Description of Related Art
Comparators of the related art are well known. For example, Donald A. Kerth's U.S. Pat. No. 4,748,418 assigned to Crystal Semiconductor, discloses a quasi-autozero technique which can remove signal hysteresis in a comparator, by momentarily shorting the comparator output to ground prior to comparison. Comparators of the related art are known to use an autozero technique employing sample and hold circuits to store the comparator offset. However, when autozero and quasi-autozero techniques are combined, circuit performance is diminished.